Variable-speed motor.



J. BURKE. VARIABLE SPEED MOTOR. APPLICATION FILED MAY 17. 1905.

913,691. 'Patented Mar. 2, 1909. 2 SHEETS-SHEET 1.

J. BURKE. YARITAABLE SPEED MOTOR. APPLICATION FILED MAY 17, 1905.

Patented Mar. 2, 1909.

2 SHEETS-SHEET 2.

potential, instead JAE/IE S BU To all whom may concern:

Be it knon that i, JAMES BURKE; a citizen oi the United States, residing at Erie, the county of Erie and State of Pennsylvania, have invented certain new and useful Improvements in =1iable--. peed Motors, 01 WlllCll the following is at full, clear, and exact specification.

My invention relates to electric machines and particularly to a form of electric motor and method of operating motor for obtainto the positive and negative brushes, the

motor will operate'at a certain speed and by connecting to the additional point of lixed of to one of the brushes named, the motor will operate. at epproxt niately twice the speed. 1 also provide means for varying the lield strength so that a series of speeds may be obtained giuluatod by small steps. Ely improved l'orm ol motor may also be used as a transformer.

Ely invention dates to my improved type ol machine ruirticularlv described in my pending application l'lUllIi-l 1' 355,564, .liled l ebruary l, MOT, and my present invention will be understood by reference to the accompanying druvvir and l'oilowing description Figure l is u dia n'am ol my improved mo tor and connections lor or crating the same at variable speuls; Fig 3 and 3 are disgrams of nwdi'licalions; Fig. l is a disgranr ol connections and development of controh ling switcn; 5 and ti are diagrams of modifications.

Referring to Fig. l. the armature winding oi the usual form for direct current gmerators is indicalod at l and the coimnutetor at 2. The machine is shown in this instance as bipolar in form having the poles 3 and positive and negative brushes l. in addition to the winding 1, 1 provide additional coils or Windings 5, 5 5 wound upon the some core and Specification of Letters Patent.

glicat'ion 27-day 1], 1205. Serial Ho. 260,859.

ERIE, EENHSYLVANEA, ASSIG"OR TO BURKE ELECTRIC COMPANY, A

ATIGN OF PENNSYLVANIA.

Latented March 2, 1909.

preferably in the same slots, one end of each of the coils being connected to the collector ring 6. The other ends of the coils are con nected to points a, l), 'c, in the armature which points in this example are 120 elec trical degrees apart. The coils are shown connected to the commutator segments, but

r they may, if desired, be connected to points in the armature winding itself. The positive and negative supply conductors are indicated at 7, S and switches 9, are shown for connecting the supply wires to positive and negative brushes 4 and to brush 11 which bears on the collector ring 6. The lield Winding 12 is connected across the supply conductors and through a variable resistance 13 for varying the strength of field.

The coils 5 5, 5, in operation generate an electromotive force which is always approximately equal to the dill'erence in poten tial between the ring 6 and the points in the armature to which the coils are respectively connected and consequently the potential of ring 6 remains pout-sully lixed at all times. For example, referring to the condition at the instant when the ports are in the position shown in Fig. l, ii the supply wires were connected to the l;-rushcs l, the potential of point a would be half way between that of the positive brush and that of the negative brush. The windings 5*, 5, 5, should each have such a number of turns that the 1naximum electromotive l'orce generated by each one will be approximately one-half the electromotivc force between the positive and negative brushes 4. By this requirement the turns in each alternating current winding should he one half the turns per circuit of the direct current winding. Since coil 5 is shown passing through the neutral field, no electromotive force will be generated by it and ring 6 'uill tlwreilore be at the same potent-ial as point a, or approximately half way between the potential 01 brushes 4. Coil 5 is connected to point I), the potential of which is between the potential of ,the negativebrush and that of the neutral point. (oil 5 is shown in such a position that it is generating a counter electromotive force equal to the dill'eronce'in potential between that of point I) and of ring 6. 'lhe potential of point 0 is below and is approaching that of the positive brush 4 and the position of coil 5 is such that it generates a counter electromotive force equal to the diil'erenc-e in potential between variety of ways.

, that of point 0 and of ring 6. Consequently each of the coils 5 5 5 tend to maintain the potential of ring 6 fixed and at a value approximately midway between that of the brushes 4. This is likewise true of each position of the armature as it rotates. Hence the windings or coils 5, 5 5, generate an alternating counter electromotive force in conjunction with the'winding 1 and these additional coils tend to maintain a point of fixed otential at ring 6 midway between that o brushes 4. s

In operating the motor, if the supply mains '7, 8 are connected to the brushes 4, the machine will operate at the usual speed and under full strength of field if all resistance 13 is cut out. The speed may now be increased by successive steps by inserting the field resistance'13, After the field is weakened to the desired degree, the resistance 13 may be cut out giving the full'fiel'd strength again and one of the switches 9, 10, say switch 10. for example, will be thrown into connection with the brush 11. This condition will give practically double the speed'obtained when the supply mains are both connected to brushes 4 and'under the same field strength. This will be understood since the counterelectromotive force generated in coils or windings 5, 5", 5, tends to maintain ring 6 at a fixed potential and at a value midway between the potential of positive and negative brushes 4 and these eoils'also serve as a path for thecurrent fron main 8 into the armature. Consequently the winding 1 or parts thereof are in effect subjected to twice the voltage received when the supply mains are connected to brushes 4. For example, in

g the position shown in Fig. 1., coil 5? is generatmg no electromotive force and point a isv therefore subjected'to the potentialof line 8 when switch 10 is connected electrically to brush 11 and the art of the winding between point a and t e positivebrush 4 is subjected to twice the voltage compared with the condition when line 8 is connected to negative brush. 4. The electromotive force generated by coils 5, 5', 5 is such as to maintain a corresponding relationship at all positions of the armature and the double speed referred to is obtained. The field strength may now be weakened again and increased speeds obtained.

I have described one form of m invention with reference to Fig. 1 and it wi l be understood that the form of the windings or coilsand their connections may be changed in a In Fig. 2 I have in icated a form of motor by which I obtain four different speeds from a single pair of supply wires and with constant field strength. '1 he supply mains are shown. at 7, 8. g The field, which may be multipolar,

is indicated at 3 and the field winding 12 isshown as a shunt winding connected across the mains 7, 8. The armature 14: is rovided with duplicate windings of the ty e escribed with reference to Fig. 1'; that is, t ere are two sets of windings not electrically connected on the armature core, each set comprising the usual direct current winding and commutator and an alternating current windin con nected thereto at displaced points an to a collector ring as above described. In Fig. 2

which will shift one pole oi the supply line, I

'may obtainfour different speeds from'the motor. The main 7 is shown connected to the brush 16, and the brushes 17, 21 are electrically'connected. In theposition shown, the switch 23 connects the supply main 8 to the brush 20. Current willthen use from one supply line to the other throng i the two commutator fwindin'gs in series.- This will give the lowest speed, which we may assume to be 100 revolutions. By shifting the switch so as to connect line 8 with the ring 22 throughthe brush bearing thereon, the speed will be increased. v force of the line is then applied to the. ring22 and brush 16, the full electromotive force of the line is applied to a part of the total Winding.. If we assume that the two sets of windings have the same number of conductors each, then with this connection three-fourths of the total conductors in the two commutator windings will receive the full potential of the line giving a speed of approximately 4/3 of 100 or 133. Upon shifting switch 23 to.

being connected to brush 16. "Tlie initial speed of the motor will now be doubled approximately, giving 200 revolutions; Fur th'er movement'of switch 23 will connect line 8 to the collcctorring 18. One half ofv one commutator winding then receives the full line electromotive force giving a speed of approximately 400 revolutions.

In Fig. 3 l have illustrated'a connection which is different from that of Fi 2 which could be used to give third speed 0%2 lutions. In the connection of Fig. 3, current from the line is introduced and taken from the motor through collector rings. This gives the very interesting. condition of a motor operated by direct current, which current is transmitted to and from the motor through slip rings. With this arrangement,

00 revo- Since the electromotive v from a single pair of supply mains halt oi eech commutator winding is connected in series with the other, the brushes 1'? and 21 being connected. Continuing the example above referred to, the speed would then be 200 revolutions approximately, since halt 01 each winding in series receives the full electroniotive force of the line. I may obtain diiierent ratios of speed from that above described by making the number of conduc 4 tors in one set of the windings dill erent from the number in the other set. T hat is, by proportioning the windings, I may vary the speed ratios as desired in particular cases.

in Fig. 4 are snown tlxe connections and development of one form of controller by which a large number of speeds are obtained 7-, 8. l The similar parts of the motor are designated by the same reference characters as are used in Figs. 2 and 3. The connections from tliemo tor extend to a series of contacts 24. adapted to engage wit. t e conducting strips 25. When toe contacts 24 are on line 26, t o slowest speed will be obtained, t e columntater windings being connected in series across the line and the field l aving; its full strength. Further movement of tie controlling switch will increase ti e speed by successively weakeningtlie lield strengtb. This is accomplished by inserting sections of tie iield resistance 27 in t1 efield circuit. This resistance is shown as being made up of thee sections connected to contacts and as the controlling switch is moved, the resistance sections are successively cut into too lield circuit on account of the step orm of tie conductor line 29, field is given its full strength and the connections re sucli ti". at one line is connected to ring 18 and tie otl or to brush 20, tliere being one 'l alt of one winding connected in series with the other winding. This .Will give a further incrcase of speed over the previous step and the speed will be again increasedby moving the controlling switch to out in tire field resistance by sections. in position on line 30, the field is given its full strength, but the increase in speed is obtained by applying the line electromotive force to each of tbe commutator windings, the latter being connected in parallel. After further increased. speeds are obtained by weakening tile field, the position on line 31 is reached which gives the field its full strength again and also connects two halves of the coinlnutator windings in parallel, the line being connected to one commutator brush and the collector ring of each winding. The maximum speed is obtained by weakening the field while maintaining tire parallel connection of the halves of the windings. id/bile I have indicated one form ot'controlling switch which gives sixteen diilerent speeds, it is evident that the form. and arrangement of the parts might be varied to give the results l f i en contact is made on vmeans comprising wit? a winding of the general form described with reference to Fig. 1 that i it l-as a commutator .windin and tne additional alternating current winding electrically connected thereto and cooperating tterewitii as above described. A twowire supply circuit 83 is connected to tile brusles bearing on tie co1n mutator and energy from s circuit serves to operate tie machine as motor. Tue outside wires 34. of a three-wire tern are connected to the commutator ln'usires or mains 33, and the neutral wire 35 connected to the brush bearing on t;.e collector ring 86 which is connected to ti... alternating curent coils. Under ti condition the mmc? ine will operate as a niotor and transform the two-wire system into a bree-n-ire dietributing system. Then tlzus operating; an a motor, tile coils connected to ring will n'iaintain tie potential of tie ring approximately constant and about i all way between thepotential of the outside wires. Lamps orot! er translating; device: may t on be connected between ti o neutral and outside wires, and tire alternating current or balancing windings will serve as a pat':. throne-it 0 machine for any unl'nilanced current and also maintain trepotential of ti 0 neutral ap roximately constant. I

Fig. 6 s: ows an arrangement in an ie-i t 0 machine operates as a rotary converter to change tic voltage. llere t- 0 supply main-= are connected, one to one commutator brush and tie otter to tee brush. engaging tie ring 36. Tue armature will rotate 21:; a motor w! en ti'us supplied. wit. 01101111 and current may be taken oll' tire comuuil'ator brushes to supply a two-wire circuit 37 its energy of double tne voltage ol t'. e supplv circuit. Also it t: c mains.37 were t e supply wires, tire mains could be supplied with energy of one-.mll 1112c voltage giving a decrease ol electromotive l'orce instead ol an increase.

My invention i susceptible of many modi fications and embodiments in various forms of construction, and I am not limited except as indicated in the following claims.

Having thus described my invention, 1 declare that what I claim as new and desire to secure by Letters Patent, is,-

1. In an electric motor, the combination with an armature winding having a co1umu tator, of brushes on the commutator for applying the line voltage to said winding, and an additional dynamo electric generating winding for applying the line voltage to a part of said first named winding.

in an electric motor, the combination i l) l) of a winding having a commutator, brushes with an armature Windinghaving a commutator, of brushes on the commutator for applying the line voltage to said winding, means comprising an additional dynamo electric generating winding for a plying the line voltage to a part of said rst named winding, and means for varying the field strength.

3. in an electric motor, the combination with an armature Winding having a commutator, of brushes on the commutator for apto one of said brushes and to said second winding for obtaining another speed.

5. In an electric motor, the combination of a winding having a commutator, brushes on said commutator, a second dynamo electric generating Winding connected to said first winding and to a collector ring, and means for connecting the supply line to said brushes and for connecting'one supply line to said ring.

6. in an electric motor, the combination on said commutator, a second dynamo electric. generating winding connected to said first winding and to a'collector rin means for connec mg the supply line to salt brushes and for connecting one supply line to said ring, and means for varying the field strength.

7 In an electric motor, an armature core, a winding thereon having a commutator, a second winding thereon having a commutator, and'means for connecting a part only of one of said windings in series with the other of said windings.

8. In an electric motor, an armature core, a Winding thereon having a commutator, a second w nding thereon having a commuta tor, and means for connecting parts only of said windings inparallel with each other.

9. In an electric motor, an armature core, a winding thereon having a commutator, a second winding thereon having a commutator, a controlling switch, and means whereby movement of the controlling switch connects said windings in series or in parallel, or con-- nects parts of said windings in series or in parallel.

10. In an electric motor, an armature core, a winding thereon having a commutator, a second winding thereon having a commutator, a controlling switch, and means whereby movement of the controlling switch connects said windings in series or in parallel,-or parts of said windings in series or in parallel, and means for varying the field strength.

11. In an electric motor, an armature core, a winding thereon having a commutator, a balancing winding on said core connected to said winding and to a collector ring, a second winding on said core having a commutator, a balancing winding on said core connected to said second winding and to a collector ring, a

controlling switch, and connections whereby movement of the controlling switch connects said windings in series or in parallel, or parts of said winding in series or in parallel.

12. The method of operating an electric motor, which consists in subjecting the electromotive force of the supply line to thecommutator brushes to obtain one speed, and

dynamically generating an electromotive forceto maintain a mint of fixed potential between that of the rushes and subjecting only part of the armature to the electromotive force of the supply line for obtaining another speed.

13L The method of operating an electric motor, which consists in subjecting the electromotive force of the supply line to a winding thereof to obtain one speed, dynamically generating a less electromotive force to maintain a point of fixed potential and subjecting only part of said winding to the electromotive force of the supply line for obtainin another speed. I

n testimony whereof I aflix my signature, in presence of two witnesses.

JAMES BURKE.

Witnesses A. O. CHAPIN, O. V. EnwAnns. 

